This invention relates to computer data storage systems. It has been estimated that an oil company, for example, would need to store about 10.sup.15 bits of data, and that the magnetic tape currently used to store this quantity of data would occupy about 8 acres. It has also been estimated that U.S. Social Security, large banks and insurance companies need about 10.sup.14 bits of storage each, and satellite and U.S. Census Bureau applications require about 10.sup.13 bits each.
Aside from the problem of storing the magnetic tape required to store these quantities of data, there is the problem of accidental alteration or erasure of the data, and the problem that magnetic tape must be re-recorded at intervals of 6 months to 3 years to avoid data loss. Additionally, tape storage is limited by slow access times.
Beam addressed memories have the potential for solving these problems. Both electron and ion beams are attractive because of their ease of deflection, potentially small spot sizes, and appreciable energy density. Two of us have previously described, in J. Vac. Sci. Technol., 15(3), pp 841-844, May/June 1978, two concepts for particle beam memories which are written with focused ion or electron beams and read with an electron beam. The end result of both writing methods is to produce small damaged or doped regions near the surface of a semiconductor pn junction. The stores information is read with a 2.5-KeV electron beam. When the focused electron beam impinges on an unrecorded area, a signal current is generated in an external diode biasing circuit. When the beam impinges upon a written area the signal is reduced. With such recording schemes, bit spacings on the order of 0.1 micron become feasible at data rates on the order of 10 Mbits/sec. This would allow very large permanent memory stores, ranging from 10.sup.12 to 10.sup.15 bits with 100 microsec block access time. For example, one data plate with an active area of 10 cm.sup.2 would equal the storage capacity of 400 rolls of magnetic tape; twenty such plates could house the files of the Social Security system.
We have found that a polymeric film implanted with heavy metal ions may be employed as the storage medium in a beam addressed memory system.
It is known to implant metal ions in a polymeric film. For example, IBM Technical Disclosure Bulletins, Vol. 14, No. 10, Mar. 1972 discloses that the temperature and corrosion resistance of cross-linkable polymer photoresist films are greatly increased by bombardment with high-energy ions.
It is an object of the present invention to provide a novel beam addressed memory system.
It is another object of this invention to provide a novel storage medium for a beam addressed memory system.
Other objects, aspects and advantages of the present invention will become apparent to those skilled in the art from a reading of the detailed disclosure and the appended claims.